improve error reports categories query on postgres

postgres can't/won't use the index for a DISTINCT query, so be a
bit more explicit with it to get it to use the index

test plan:
 * go to /error_reports
 * it should load fast, there should be a categories dropdown,
   and it should have a few things in it besides all categories
   (assuming you have some error reports)

Change-Id: If7c71cd669e7eadc1792eefe1fb6e85a08c054ed
Reviewed-on: https://gerrit.instructure.com/8190
Reviewed-by: Brian Palmer <brianp@instructure.com>
Tested-by: Hudson <hudson@instructure.com>

Author: ccutrer

app/models/error_report.rb

@@ -137,6 +137,20 @@ def self.useful_http_env_stuff_from_request(request)
     stuff
   end
 
+  def self.categories
+    if ActiveRecord::Base.configurations[RAILS_ENV]['adapter'] == 'postgresql'
+      categories = []
+      category = ErrorReport.minimum(:category)
+      while category
+        categories << category
+        category = ErrorReport.minimum(:category, :conditions => [ 'category>?', category ])
+      end
+      categories
+    else
+      ErrorReport.find(:all, :select => 'DISTINCT category', :conditions => 'category IS NOT NULL', :order => 'category').map(&:category)
+    end
+  end
+
   on_send_to_external do |error_report|
     config = Canvas::Plugin.find('error_reporting').try(:settings) || {}
 

app/models/user.rb

@@ -20,7 +20,7 @@ class User < ActiveRecord::Base
   # this has to be before include COntext to prevent a circular dependency in Course
   def self.sortable_name_order_by_clause(table = nil)
     col = table ? "#{table}.sortable_name" : 'sortable_name'
-    connection_pool.spec.config[:adapter] == 'postgresql' ? "LOWER(#{col})" : col
+    ActiveRecord::Base.configurations[RAILS_ENV]['adapter'] == 'postgresql' ? "LOWER(#{col})" : col
   end
 
   include Context

app/views/errors/index.html.erb

@@ -3,16 +3,14 @@
   add_crumb t("#crumbs.error_reports", "Error Reports")
 %>
 
-<% unless params[:action] == 'show' %>
 <% form_for @current_user, :url => '/error_reports', :html => { :method => :get }  do |f| %>
   <%= t :message_contains, "Message contains" %>
   <input type="text" name="message" value="<%= @message %>" style="width: 250px;"/>
   <select name="category">
-    <%= options_for_select(([[t(:all_categories, " - All Categories -"), nil]] + ErrorReport.all(:select => 'DISTINCT category').map(&:category)).compact, params[:category]) %>
+    <%= options_for_select([[t(:all_categories, " - All Categories -"), nil]] + ErrorReport.categories, params[:category]) %>
   </select>
   <button type="submit" class="button"><%= t "#buttons.search", "Search" %></button>
 <% end %>
-<% end %>
 
 <% content_for :pagination do %>
  <% if params[:action] == 'index' %>

spec/models/error_report_spec.rb

@@ -51,4 +51,16 @@
   it "should not fail with invalid UTF-8" do
     ErrorReport.log_error('my error', :message => "he\xffllo")
   end
+
+  it "should return categories" do
+    ErrorReport.categories.should == []
+    ErrorReport.create! { |r| r.category = 'bob' }
+    ErrorReport.categories.should == ['bob']
+    ErrorReport.create! { |r| r.category = 'bob' }
+    ErrorReport.categories.should == ['bob']
+    ErrorReport.create! { |r| r.category = 'george' }
+    ErrorReport.categories.should == ['bob', 'george']
+    ErrorReport.create! { |r| r.category = 'fred' }
+    ErrorReport.categories.should == ['bob', 'fred', 'george']
+  end
 end